What’s Killing Florida’s Palm Trees?

An “unknown but growing number” of sabal palms in the Tampa Bay area are being killed by the disease, which has left scientists “stumped,” the Associated Press reports. Even after identifying the disease, scientists will have to track down the insect responsible. The process could take many years.

Experts are pessimistic about the fate of the trees. Tim Schubert of Florida’s Division of Plant Industry told AP that the disease causes infected trees to slowly lose their leaves. Pathologist Monica Elliot added that the disease is a tough diagnosis, often confused with nutrient deficiencies or excessive trimming.

Experts do know that the disease is a phytoplasma, a type of bacteria that lacks a cell wall. But further confirmation of the disease requires “expensive DNA tests,” according to the St. Petersburg Times.

The state’s research efforts are being stymied by a tight budget, though the use of emergency funds is being considered.

Florida’s challenge is concurrent with a mountain pine beetle infestation in the western U.S. and Canada, mostly affecting lodgepole pines, and treatable with a temporary dose of pheromones that wards off new beetle colonies.

The process of the sabal palm’s disease can resemble other conditions. “First to go are the lower leaves in the tree’s canopy, followed by a dead spear leaf. Finally, the palm’s canopy collapses.” Other Florida trees are also suffering from disease, with citrus trees being attacked by canker and greening. Experts have not found a cure for either of those conditions.

Scientists suspect that the phytoplasma is spread by “plant-hopping insects that feed on the trees’ nutrient-carrying tissue.” Forest extension agent Rob Northrop told the Times that the trees lost will likely have a larger impact. “The loss of these palms could change the interaction in the forest, the soil, the water, the animals, not to mention the landscape value of the palms in cities like Tampa.”

The Detroit News reported earlier in July on the growing number of states affected by the emerald ash borer, an Asian beetle that has killed millions of ash trees from Indiana to New Jersey. The spread “is caused as much by dummies moving infected ash tree firewood all over the place as by the spread of the insect itself,” Jeff Ball writes. Once gone, the ash trees are often replaced by “junk plants” that prevent the growth of trees.

In western states, the mountain pine beetle has been ravaging lodgepole pines and some other pine species, killing more trees than wildfires in 2007 and so far in 2008. The beetles are being combated with a pheromone treatment that makes beetles believe the trees are already infested with other colonies and thus pass them by.

The University of Florida research center at Fort Lauderdale compiles information about palm conditions and diseases on its Web site, including the state’s history of various conditions and details about symptoms and treatments.